The agency announced in March that it favored a 100-acre site in north St. Louis for the new headquarters. St. Clair County in Illinois had offered a 182-acre greenfield site adjacent to Scott Air Force Base.

The choice was a major win for the city of St. Louis, which has made the effort to retain the federal spy agency — and its 3,100 jobs — its No. 1 economic development priority. After another billion-dollar project, the Mississippi riverfront stadium, fell through, the city was also desperate for a catalyst on the north side, which has been in economic distress for decades. The NGA will move from a facility in Soulard in 2021.

Illinois officials had urged the agency to reconsider its assessment of the security and environmental impact of the proposed sites, claiming those elements were not studied properly.